DNA sheds light on a new member of the human family.

A recent article by Jamie Shreeve in National Geographic magazine provides a fascinating insight into the history of the human race and its relationship with our more primitive ‘cousins’; the Neanderthals and the Denisovans.

Russian archaeologists from Novosibirsk performed excavations in the Denisova cave in the Altay Mountains of southern Siberia. Their work revealed evidence that all three groups – modern humans, Neanderthals and Denisovans – co-existed in the area at some time between 50,000 and 30,000 years ago. The story begins with the find of a bracelet of polished green stone, certainly the work of modern humans, in strata in the floor of the cave termed Layer 11. Further excavations in Layer 11 brought to light a tiny bone which turned out to be from the little finger (pinkie) of a human. DNA analysis by researchers under Svante Pääbo at the Max Planck Institute in Leipzig, one of the world’s leading experts in ancient DNA, gave the surprising result that the pinkie belonged to a young Denisovan girl.

The discovery of the pinkie bone was followed by that of two teeth which also proved to be Denisovan. Then in 2010, DNA analysis of a human toe bone, again from Layer 11, indicated that it belonged to a Neanderthal.

National Geographic presents a possible model for the history of the three races. Some half a million years ago, in Africa, the closely related Neanderthals and Denisovans diverged from our common ancestor Homo heidelbergensis. On leaving the African continent the Neanderthals migrated into Europe while the Denisovans moved east into Asia. In turn a small group of modern humans migrated out of Africa between 70,000 and 40,000 and met with and mated with the Neanderthals and Denisovans.

We now know that the Neanderthals and Denisovans have vanished from the planet and only our race, homo sapiens, exists today. However, traces of their DNA survive in modern humans. Some 2.5% Neanderthals DNA is found in all non- African humans while the DNA in Australian aborigines is 5% Denisovan. This story provides evidence that the evolution of the modern human is not linear but it is much more complex than we could ever imagine.